The present invention relates generally to image forming devices, and more particularly to a printer that automatically separates self-adhesive portions of print media from a continuous strip of protective backing without causing excessive looping or jamming of the printer.
Self-adhesive labels have been in use for many years. Typically, self-adhesive labels come on a continuous strip, such as in a roll, and have a front side suitable for writing or printing information, an adhesive back side, and a protective backing forming the strip and adhering to the adhesive back side of the labels. Before using the printed labels, the labels must be peeled away from the protective backing and adhered to a medium, e.g., an envelope or a box, for labeling.
Conventional devices designed to print information on the self-adhesive labels and automatically peel off the printed (or imaged) labels from the protective backing include the Eltron LP-2042 printer. Typically, the continuous strip of the labels enters a conventional device, such as a printer from a first location of the devicexe2x80x94normally the back side of the device. After entering, the strip passes through a contact area between a print head and a platen of the device, and then leaves the device from a second location-normally the front side of the device. Ideally, the printed (or imaged) labels should be peeled off from the protective backing strip as it leaves the device. Unfortunately, when certain printing processes (such as thermal transfer) and/or small media are used, conventional devices tend to fail when the protective backing forms a loop between the print head and an exit roller (which directs the protective backing out of the devices). Such failure may occur before and/or after the labels have been removed from the protection backing and may generally result in either the labels failing to detach and following the protective backing through the exit roller, or the labels only partially separating and adhering to the exit roller.
Other types of conventional devices do not automatically remove the protective backing from the labels and require the user to manually peel the protective backing off the printed labels. Such devices, however, are inconvenient for users and ifficient in today""s busy world. Even so, these devices are also not immune from the above-noted looping problems.
An object of the present invention is to provide an image forming device that will automatically separate detachable adhesive print media from a continuous protective backing strip without causing excessive looping or jamming to the image forming device.
One embodiment of the present invention provides an image forming device, e.g., a printer, comprising a print head; a platen for pressing a print medium, such as a sheet of paper or a series of self-adhesive labels attached to a continuous protective backing strip, against the print head and for moving the printing medium during operation; a stripper bar properly angled upward and adapted to separate the self-adhesive labels from the protective backing strip when it passes over the stripper bar; and a stripper roller positioned under the stripper bar. Initially the stripper roller causes the protective backing strip to pass under the stripper roller at a first speed sufficiently different from a second speed of the label strip passing between the print head and the platen to prevent looping or jamming of the protective backing and label strip.
In a preferred embodiment, the roller includes a stepped stripper roller shaft encircled by a sleeve and adapted to cause the protective backing strip to initially pass between the stripper roller and the platen at a first speed sufficiently different from a second speed of the strip passing between the print head and the platen until the tension on the protective backing strip reaches equilibrium which equalizes the first and second speeds of the protective backing strip respectively. The stepped roller shaft is also adapted to prevent looping of the protective backing strip when used in conjunction with narrow print media.
The foregoing and additional features and advantages of this present invention will become apparent by way of non-limitative examples shown in the accompanying drawings and detailed description that follow. In the figures and written description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawing figures and the written description.